Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual é a margem média que possui uma rodada de 13. (h)?
 ###Tabelas: CREATE TABLE national_team_goals (national_team_goals_id AUTO_INCREMENT PRIMARY KEY, Goal INT, Date VARCHAR, Venue VARCHAR, Score VARCHAR, Result VARCHAR, Competition VARCHAR) CREATE TABLE doubles:_13_9_titles_4_runners-up (doubles:_13_9_titles_4_runners-up_id AUTO_INCREMENT PRIMARY KEY, Outcome VARCHAR, Year VARCHAR, Championship VARCHAR, Surface VARCHAR, Partner VARCHAR, Opponents VARCHAR, Score VARCHAR) CREATE TABLE winning_head_of_the_river_championship_events (winning_head_of_the_river_championship_events_id AUTO_INCREMENT PRIMARY KEY, Crew INT, Open 1st VIII VARCHAR, Open 2nd VIII VARCHAR, Open 3rd VIII VARCHAR, U16 1st VIII VARCHAR, U16 2nd VIII VARCHAR, U16 3rd VIII VARCHAR, U15 1st Quad VARCHAR, U15 2nd Quad VARCHAR, U15 3rd Quad VARCHAR, U15 4th Quad VARCHAR, U15 5th Quad VARCHAR, U15 6th Quad VARCHAR) CREATE TABLE draft_selections (draft_selections_id AUTO_INCREMENT PRIMARY KEY, Round INT, Pick INT, Position VARCHAR, Nationality VARCHAR, School/club team VARCHAR) CREATE TABLE home_and_away_rounds (home_and_away_rounds_id AUTO_INCREMENT PRIMARY KEY, Round VARCHAR, St Kilda Saints VARCHAR, Opposition VARCHAR, Their Score VARCHAR, Margin INT)  
SELECT AVG Margin FROM home_and_away_rounds WHERE Round = 13. (h)